The present invention relates to the field of flat display technology, and more particularly to a thin-film transistor array substrate for AMOLED and a manufacturing method thereof.
A conventional Active-matrix organic light emitting diode (hereinafter, abbreviated as “AMOLED”) display apparatus generally includes a substrate, a plurality of thin-film transistors formed on the substrate, and an organic light emitting diode body formed on each of the thin-film transistors. Specifically, the AMOLED display apparatus, in one pixel, has a switching thin-film transistor and a driving thin-film transistor. The switching thin-film transistor is used to address a pixel voltage (i.e. gate driving voltage). The driving thin-film transistor is used to control a driving current of the organic light emitting diode body.
When manufacturing an AMOLED display apparatus, a gate insulator of the switching thin-film transistor and a gate insulator of the driving thin-film transistor are formed simultaneously with the same thickness, which causes the switching thin-film transistor and the driving thin-film transistor to have the same gate capacitance. A sub-threshold swing (S.S.) of a thin-film transistor depends on the gate capacitance; and the gate capacitance further depends on the thickness of the gate insulator. Thus, when the gate insulator of the switching thin-film transistor and the gate insulator of the driving thin-film transistor are formed with the same thickness, the switching thin-film transistor and the driving thin-film transistor will also have the same sub-threshold swing.
However, the switching thin-film transistor requires a small sub-threshold swing to achieve an object of fast charging/discharging; and the driving thin-film transistor requires a relatively large sub-threshold swing to facilitate display of grayscale images. Thus, in the condition that the switching thin-film transistor and the driving thin-film transistor have the same sub-threshold swing, a relatively small sub-threshold swing will be disadvantageous to the AMOLED display apparatus on displaying grayscale images; and a relatively large sub-threshold swing will lower the speed of charging and discharging, and thereby affecting the operation speed of display circuits. Thus, there is a conflict existing between the sub-threshold swing of the driving thin-film transistor and the sub-threshold swing of the switching thin-film transistor.
Furthermore, in the AMOLED display apparatus, electrodes which are perpendicularly crossed may be easily short-circuited under an unstable manufacturing process, and the parasitic capacitance formed at the electrodes and insulating layers therebetween is disadvantageous to higher-order display.
Hence, it is necessary to provide a thin-film transistor array substrate for AMOLED and a manufacturing method thereof to overcome the problems existing in the conventional technology.